The use of so-called insertable module technology is known from the field of power distribution and in motor switching units, in other words low-voltage switchgear assemblies for motor branch circuits, the main task of which is to control and protect motors in industrial processes. Every motor branch circuit here is inserted into its own truck module. These truck modules can then be positioned in the manner of drawers in correspondingly provided truck slots. Such motor switching units are also referred to as motor control centers (MCC).
Motor branch circuits can be embodied differently for specific applications. A direct starter, a reversing starter, a star-triangle starter, etc. can be provided from the primary current side. From the control current side the connections to the local control point, the displays, the delay systems, the locking systems, etc. can vary. Despite these different functionalities, the truck modules have the same external structure. Both the external dimensions and the electrical interfaces of the truck modules are a function of the specific characteristics of the motor branch circuit in the interior of the truck module. This can very easily result in incorrect assembly, for example when a motor branch circuit has to be replaced for example due to a short circuit or the end of the service life of the contactors or the circuit breaker. Operational failure or damage to the assembly as a whole can be the result of incorrectly replaced truck modules. It is therefore essential to exclude such confusion reliably, in particular for safety-related motor branch circuits.
To prevent confusion, mechanical coding of the truck modules is known from the prior art. Mechanical coding plugs or coding facilities are deployed here on both components, with the intention of preventing incorrect combination of truck module and truck slot. One disadvantage of the deployment of such coding plugs is however that they only allow a relatively small number of coding options. It is therefore not possible to exclude the risk of incorrect assembly completely in the case of switchgear assemblies with a large number of insertable modules. Also as well as the identification outlay when producing the truck modules there is also a considerable logistics outlay as well as the inspection and test outlay during commissioning, with the result that high preparation and maintenance costs are incurred.